Raw material delivery system for compacting press

ABSTRACT

A raw material delivery system is disclosed. It is used with a press of the type used to compact raw material in a die. The press has a horizontal table with an opening in which the die is held. A feed shoe is movable across the table between an extended position where a central bore of the feed shoe overlies the die and a retracted position. In one embodiment, a vertically movable feed tube is carried on a bridge, and has a passage through which raw material may pass. The vertically movable feed tube receives raw material from a vertically fixed feed tube received telescopically within the vertically movable feed tube. A valve is between the two feed tubes. A valve may be provided between the bridge and the feed shoe so that the raw material passes through this interface without being exposed to cross-ventilation. The vertically movable feed tube may be pivotally connected to the bridge so that the movable feed tube may be pivoted away from the bridge opening when it is desired to change the metal powder or the die. Both the fixed and movable feed tubes may be heated, and heated material may be received by the fixed tube. In another embodiment, a heated flexible hose extends from the vertically-fixed tube to the feed shoe.

This is a continuation-in-part of U.S. patent application Ser. No.08/768,977, filed on Dec. 18, 1996, now U.S. Pat. No. 5,858,415, whichis incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to a system for delivering raw material toa compacting press, and more particularly, to a system for heatingpowdered metal and delivering the heated powdered metal to a die forcompaction into a green metal part.

BACKGROUND OF THE INVENTION

It is known to produce metal parts by compacting powdered metal andheating the compacted metal powder to sinter the metal particles toproduce a finished metal product. However, such products are known tohave lower densities than comparable wrought metal products. To achievegreater densities, products have been subjected to secondary operations,such as using a second coining operation.

Recently, there has been interest in the use of a compacting press tomanufacture metal parts from metal powders where the metal particles arecoated with a thin polymer lubricant. The polymer coatings are believedto lubricate the interfaces between metal particles and forming toolsurfaces thereby making it easier to form workpieces due to decreases inthe internal friction and stresses created during compaction. Firstlevel workpieces using conventional lubricated powders have beencompacted into workpieces having final densities in the range of 6.8-7.1grams per cubic centimeter (g/cc) when compacting at pressures of 35-60TSI. To obtain higher densities, over 7.2 g/cc, a workpiece is typicallyfirst green-formed using lubricated powders to a density of about 6.8,and then pre-sintered to a temperature typically between 1400 and 1700degrees Fahrenheit (° F.) in order to burn out the lubricants, relieveinternal stresses, and to promote mechanical bonding. Next, theworkpiece surface is coated with a lubricant and pressed a second timeto reach the preferred density range. As can be appreciated with suchlevel 2 and 3 workpieces, reaching higher density levels becomes costlyand time-consuming; moreover, there may be density fluctuations in theworkpiece after the second pressing. And while advancements in the useof lubricants and other materials have allowed for production ofworkpieces with increased densities without resorting to secondaryoperations, pressing a room-temperature lubricated powder to a densityin the range of 7.1 g/cc has its price: for example, the compressiveforces are typically very high in such operations, on the order of atleast 100,000 psi, and the wear of the tools is accelerated; moreover,with the much higher compressive forces needed to reach these densities,the workpieces can develop surface irregularities from the extremeinternal stresses.

More recent discoveries have found that pre-heating the polymerlubricated products has helped not only to obtain higher densities atlower compacting pressures, but also to achieve homogeneous workpiecedensities. Homogeneous workpiece density levels greater than 7.4 g/cccan be obtained. Generally, by using warm lubricated metal powders, ithas been possible to increase densities by about 0.2 g/cc whileeliminating the second coining or pressing operation.

However, problems have arisen with the apparatus necessary to heat thepolymer-coated metal powder and deliver the warm powder to the die inthe compacting press. When heated to a temperature just below a criticalpowder temperature (about 300 degrees Fahrenheit) prior to loading thematerial into the die cavity, the heated powder may become tacky andcoagulate. Typical powder delivery systems have used flexible,accordion-pleated hoses for transferring powder to the die cavity; butwhen such hoses are used with warm powder, the powder may gather in theinterstices of the pleats, become compacted and block the hose. Sincethe usual production method requires accurate gravity-controlled fillingof the powder into the die cavity from a delivery shoe, any coagulationor tackiness of the coated powder can cause variations in the amount ofpowder that is actually deposited in the die cavity. Other problems mayresult from the tacky powder creating blockage in the powder deliverysystem. In addition, conventional flexible hoses and seals may degradeor be destroyed when exposed to the elevated temperature of the warmpowder.

One attempt to solve these problems in the art is shown in U.S. Pat. No.5,213,816 (1993) to Smyth, Jr. et al. In that patent, which discloses anauger conveyor assembly and a shuttle assembly, the auger assembly has ahorizontal tube with an interior auger which is fed powdered metalthrough a vertical tube. These parts are heated. The discharge end ofthe heated horizontal tube overlies a heated hopper in the shuttleassembly, and the heated metal powder is dropped into the shuttle hopperand to a heated ring. This design has problems associated with itsoperation. First, the heated powder drops through the air from thedischarge end of the horizontal tube to the hopper, allowing the metalpowder to cool, and in the case of mixtures of different metal powders,to separate into a less homogeneous mixture. In addition, to change themachine over from one type of metal powder to another may be difficultand time-consuming. Changing the die in the compacting press may also bedifficult because of the presence of the shuttle assembly.

SUMMARY OF THE INVENTION

The present invention provides a system for delivering raw material to adie cavity in a compaction press. The raw material may be delivered atroom temperature or it may be heated before delivery. In either case,the raw material is not compacted before delivery to the die cavity, andthere is minimal opportunity for the raw material to coagulate. Warm rawmaterial may be delivered without degradation and without cooling byexposure to cross-ventilation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of an embodiment of the raw material deliverysystem of the present invention.

FIG. 2 is a partial front elevation of the embodiment of FIG. 1.

FIG. 3 is a partial cross-section taken along line 3—3 of FIG. 2.

FIG. 4 is a partial cross-section, taken along line 4—4 of FIG. 2.

FIG. 5 is a top plan view of the bridge of the embodiment of FIG. 1,with parts removed for clarity.

FIGS. 6A-6E are partial side views, taken along the same lines as FIGS.3 and 4, showing the varying positions of the feed shoe and press table,and showing filling and delivery of raw material.

FIG. 7 is a partial perspective view, with parts removed for clarity, ofanother embodiment of the invention, showing the press table, feed shoe,bridge and flange.

FIG. 8 is a top plan view of the embodiment of FIG. 7.

FIG. 9 is a perspective view of the removable heated hopper of theembodiment of FIGS. 7 and 8.

FIG. 10 is a top plan view of one embodiment of the fixed feed tube,valve and actuator of the present invention.

FIG. 11 is a cross section taken along line 11—11 of FIG. 10.

FIG. 12 is a top plan view of the fixed apertured member of the valve ofFIG. 11.

FIG. 13 is a top plan view of the pivotal end gate of the valve of FIG.11.

FIG. 14 is a top plan view of the pivotal ring of the valve of FIG. 11.

FIG. 15 is a cross-section, taken along line 15—15 of FIG. 10, showingthe vertically fixed feed tube alone.

FIG. 16 is a cross-sectional view, taken along a central plane of analternative embodiment of a pre-heater that may be used with the presentinvention.

FIG. 17 is a cross-section taken along line 17—17 of FIG. 16.

FIG. 18 is a side elevation of an alternate embodiment of the rawmaterial delivery system of the present invention, with part shown incross-section, and with parts removed for clarity.

DETAILED DESCRIPTION

According to the invention, there is provided a raw material feed systemgenerally designated 10 in the accompanying drawings. It is useful inconjunction with a compacting press machine, such as those typicallyused in powder metallurgy applications. In such powder metallurgyapplications, compacting press machines generally include a table 12with a die cavity 14 in a die 16. Generally, powdered metal is placed inthe die, and press elements compact the powdered metal to produce a rawproduct that is then sintered to produce a final product, as is wellknown in the art. To eject the part from the die 16, the table 12 of thepress generally lowers from the plane shown in FIG. 1 and the product isejected from the die.

As understood by those skilled in the art, it is necessary to get theproper quantity of raw material in place in the die 16 before thecompaction process begins. The present invention addresses the need foran improved apparatus for delivering the raw material, which may bepowdered metal, to the die.

As illustrated, raw material such as powdered metal may be delivered tothe delivery system of the present invention through an augered feeder18, as typically done in the art. The delivery system of the presentinvention may be used with either traditional cold feed systems or withwarm feed systems. The embodiment of FIG. 1 is a warm powder deliverysystem, having a pre-heater 20 which receives powdered metal from thedischarge end of the augered feeder 18 or other feed mechanism. From thepre-heater, or from some other source, the powdered metal may be gravityfed to a vertical feed tube 22, which is open at its top end 23 and hasa valve 24 at its lower or bottom end 26, with an open passage 27between them, as shown in FIG. 4. The vertical fixed feed tube 22 isfixed against vertical movement by its attachment to a suitable supportstructure, as will be understood by those skilled in the art. The valve24 is attached to the vertical fixed feed tube and is thereby alsovertically fixed. When the valve 24 is open, the warm powdered metal isgravity fed from the fixed feed tube 22 through the valve 24 into avertically movable feed tube 28. The vertically movable tube 28 has twosections, a first section 30 that is coaxial with the fixed verticalfeed tube 22 and a second integral section 32 that has a centrallongitudinal axis 33 that intersects the central longitudinal axis 88 ofthe first section 30 at an obtuse angle, as shown in FIG. 4.

In the first illustrated embodiment, the vertically fixed feed tube 22and valve 24 are telescopically received within the first coaxialsection 30 of the vertically movable feed tube 28. The verticallymovable feed tube 28 is free to move upward and downward with the upwardand downward movement of the table 12 of the compacting press. As itdoes so, its first section 30 reciprocates on the fixed feed tube 22 andvalve 24. It is desirable that the valve 24 extend beyond the top freeend 34 and into the vertically moveable feed tube 28 throughout thecycle. The vertically movable tube's 28 opposite bottom end 36 is fixedto move with the table 12. In the first illustrated embodiment, thebottom end of the vertically movable tube 28 is fixed to a bridge 38that is fixed to the top surface of the table 12. Thus, the entirevertically movable tube 28 moves with the table, reciprocating on thefixed tube 22 and valve 24 as it travels up and down.

In the first illustrated embodiment, the bottom end 36 of the verticallymovable feed tube 28 has a circular opening 40 through which the rawmaterial may be gravity fed. The bottom circular opening 40 is connectedwith a circular opening 42 at the top end 34 of the vertically movabletube 28 so that raw material received through the valve 24 may travelthrough the tube 28. The interior walls 44 of the tube 28 are smooth,without corrugations or pleats so that there are no crevices where theraw material could collect and coagulate; instead, there is a smoothinterior passage 45 through the tube 28. The vertically movable tube isrigid, and may be made out of steel, as in the first illustratedembodiment, or a similar material that can withstand the temperatures towhich the raw material is to be heated if used to deliver warm rawmaterial. In the first illustrated embodiment, the vertically movabletube 28 has an outer wall 46 that is spaced from the inner walls 44 inthe second section 32 of the vertically movable tube 28 to define acavity 48 within which heated oil may be circulated to warm the contentsof the tube 28. As shown in FIG. 1, an oil inlet 50 is formed in theouter wall 46 near the bottom end 36 of the tube 28 and is connectedthrough an inlet conduit 52 to a source of heated oil 54. An oil outlet56 is formed upstream of the inlet 50 near the top 34 of the tube 28.The outlet 56 is connected to an outlet conduit 58 which returns oil tothe source 54 of heated oil for heating and recirculation through theheating system. There may be a series of baffles 60 in the cavity 48 toforce the heated oil to flow through a circuitous path between the inletand the outlet, as shown in FIG. 4.

The bridge 38 of the first illustrated embodiment includes a horizontaltop plate 70 spaced above and parallel to the table 12. The bridge topplate 70 is connected to and supported on a pair of side walls 72. Theside walls 72 may be connected to the table 12 directly, or to a wearplate 74 that is removably attached to the table top 12 to protect thetable top from damage.

As illustrated in FIGS. 2 and 3, the vertically movable feed tube 28 ofthe first illustrated embodiment is connected at its bottom end 36 to aflat annular flange 76 that has flat top and bottom surfaces. The flange76 has a central opening 78 that is coaxial with and generally of thesame diameter as the bottom opening 40 in the vertically movable feedtube 28 so that material moving out of the feed tube passage 45 can movedirectly through the flange opening 78. The flat bottom face of theflange 76 may rest against the top surface of the bridge top plate 70 oragainst some intermediate member.

The flange 76 of the first illustrated embodiment is affixed to the endof the feed tube 28 so that there is no relative movement between theseparts, but the flange 76 and the connected feed tube 28 may swivel or bepivoted on the bridge plate between three possible positions. As shownin FIG. 5 at “A”, the flange 76 and feed tube 28 may be aligned with acentral circular opening 80 in the top plate 70 of the bridge for normaloperation wherein the raw material flows from the feed tube 28 throughthe flange opening 78 and circular opening 80. The circular opening 80extends through both the bottom and top faces of the bridge top plate 70so that the raw material may travel down through the bridge. When it isdesired to block the path of the raw material coming through the feedtube 28, such as when the die is being changed, the flange 76 and feedtube 28 may be pivoted to the position shown in FIG. 5 at “B” where thesolid top plate 70 of the bridge blocks the end opening 40 of the feedtube and flange opening 78. When it is desired to change the rawmaterial and drain the old raw material from the system upstream of theflange 76, the flange and feed tube 28 may be pivoted to the positionshown in FIG. 5 at “C”, where the feed tube opening 40 and flangeopening 78 are aligned over a cut-out 82 at the rear edge of the topplate 70 of the bridge. The edge of the cut-out 82 can be chamfered tohold the rim of a drain cup 84 that will receive and hold the drainedraw material.

As shown in FIG. 5, the flange 76 and vertically movable feed tube 28are pivotable between the “A”, “B” and “C” positions about a pivot 86that may be a rivet, bolt, or other means for pivotally mounting thebottom end of the feed tube on the horizontal plate so that the bottomopening can be pivoted to a delivery position aligned with the platebore and can be pivoted to a drain position wherein the bottom openingis spaced from the plate bore. In the illustrated embodiment, the axisof the pivot 86 is co-linear with the central vertical axis 88 of thefirst vertical section 30 of the vertically movable feed tube 28 whichis coaxial with the central vertical axis 90 of the fixed tube 22 andvalve 24.

To hold the flange and vertically movable tube 28 in the operableposition shown at “A” in FIG. 5, a plurality of clamps 92 may beattached to the top plate 70 of the bridge. In the first illustratedembodiment, the clamps 92 are pivotable about an axis spaced from thepath of movement of the flange, and extend over the flange, and may betightened against the flange to hold it down against the top plate ofthe bridge, to keep raw material from leaking out of the flange/topplate interface and to limit pivoting of the flange. A suitable type ofclamp is a thumb toggle clamp with quick release levers, although anykind of quick release clamp may be used.

Beneath the bridge 38 the first illustrated raw material delivery systemprovides a feed shoe 100. As shown in FIG. 3, the feed shoe has acentral bore 102 extending through its height that serves as a hopperfor holding raw material. The feed shoe is designed to reciprocatebetween two positions: a retracted position, as shown in FIGS. 6A,6C-6E, where the central bore or shoe hopper 102 is aligned beneath thebores 78, 80 of the flange 76, and bridge top plate 70 to receive rawmaterial delivered through the bottom hole 40 of the vertically movablefeed tube, and an extended position, as shown in FIG. 6B, where the shoehas moved horizontally across the table 12 or wear plate 74 to where thecentral bore or shoe hopper 102 is aligned over the die 16 so that theraw material falls from the central bore or shoe hopper 102 into the diecavity 14.

The illustrated feed shoe 100 has a main body 104 which surrounds thecentral bore 102 and two feed shoe tails 106 extending rearwardly fromthe main body. The feed shoe tails 106 may be pivotally connected to aclevis-shaped connected arm assembly 108 as shown in FIG. 1 which may beconnected to a device that imparts reciprocating motion to the feedshoe, such as a ball screw feeder device (not shown). An appropriateball screw device may be one supplied by Allen-Bradley Co., of HighlandHeights, Ohio and Lebanon, N.H. as Model ETS32. It should be understoodthat this identification is for purposes of illustration only; anydevice that will impart controlled reciprocating motion may be used.

Since the feed shoe has surfaces that move with respect to the bridgeand the table, it is preferred that seal structures be provided to limitor prevent leaks at these interfaces, and to prevent cross-ventilationthat could cool the warm metal powder. In the illustrated embodiments,the bridge seal 110 comprises an annular “Teflon” brand type of flexiblesealing ring 112 secured to an annular metal backing ring 114. Thesealing ring and metal backing ring 112, 114 are suspended from beneaththe top plate 70 of the bridge 38, between the bridge and the topsurface of the main body 104 of the feed shoe. Both the sealing ring andbacking have openings 113, 115 aligned with the bore 80 in the top plate70 to provide a path for passage of the raw material to the feed shoebore 102. A plurality of recesses 116 are formed in the metal backingring 114, with springs 118 disposed in the recesses. The springs 118 actagainst the underside of the top plate 70 of the bridge and the metalbacking ring 114 and serve to push or bias the sealing ring 112 againstthe top plate or surface 120 of the feed shoe main body 104 to create aseal. Thus, the top surface 120 of the feed shoe acts as a valve for thebridge seal, and allows the feed shoe cavity 102 to fill when in theretracted position under the bridge assembly. As shown in FIG. 3, thereis a small annular gap 122 between the metal backing ring 114 and theunderside of the bridge top plate 70 to allow for some height variation.To block the gap 122 and prevent raw material from leaking out throughthis gap 122, an annular liner 124 is provided in the central circularopening 80 in the bridge top plate 70. The liner 124 extends past theunderside of the bridge top plate and toward the sealing ring 112 tocover the gap 122. The liner 124 may have a top surface received in achamfer in the bridge top plate 70. The bridge top plate opening 80 maybe chamfered and the liner 124 may have a lip to fit the chamfer tosuspend the liner 124 from the plate 70. To prevent the bridge seal 110from falling from the top plate 70, it may be suspended by bolts thatlimit the size of the gap 122.

The bridge top plate 70, liner 124 and bridge seal 110 all serve toenclose the path between the bottom opening 40 of the vertically movablefeed tube 28 and the central bore 102 of the feed shoe 100. Thus, theheated metal powder may pass from the feed tube 28 to the feed shoe 100free from exposure to a cross-flow of air, and the temperature of theheated metal powder is maintained. Other seal structures that enclosethe path to provide a seal against cross-flow of air between the feedtube 28 and feed shoe 100 may be used and are within the scope of theinvention.

In the illustrated embodiment, the main body 104 of the feed shoe 100 ismade of aluminum. The illustrated top plate or surface 120 is a groundsteel plate.

The second seal is a table seal or wiper 130 comprising an annular“Teflon” brand type of sealing wiper ring 132 acting against the surfaceof the table 12 or wear plate 74. The annular sealing ring 132 isconnected to an annular metal backing plate 134 that is secured to theunderside of the main body 104 of the feed shoe 100. The openings orbores in the sealing ring and metal backing plate are aligned with thebore 102 of the feed shoe to provide a path for the raw material to passthrough the table seal to the die cavity 14 when the feed shoe isproperly aligned over the die cavity.

For applications using heated powder, the material used for the rings112, 132 is preferably one that will be stable up to temperatures ofabout 450° F. Any material that will withstand this temperature andprovide the desired seal may be used. For example, a steel sealing ringcould be used. Although it may be possible to use a one-piece combinedbacking and sealing ring for the illustrated two pieces 112, 114 and132, 134, it is preferable to use a separate sacrificial sealing ringthat may be easily replaced as it becomes worn.

It may be desirable, if the raw material is to be delivered warm to thedie cavity, to provide for heating the feed shoe central bore or hopper102. Two alternative shoes are illustrated for this purpose. In thefirst embodiment, the solid main body 104 of the feed shoe surroundingthe hopper 102 has a plurality of fluid flow paths 140 through which amaterial such as hot or warm oil may be circulated to warm the hopperand its contents. In the illustrated embodiment, the fluid flow paths140 comprise two interconnected planar paths, one above the other. Thepaths may be formed by boring four linear intersecting paths at eachlevel and then blocking the ends of the paths between the points ofintersection and the outer surfaces of the body. A fluid inlet 142 andfluid outlet 144 may be provided along the rear face 146 of the body 104and connected by fluid inlet 148 and outlet 150 conduits to the sourceof hot oil 54 for a continuous source of recirculating oil.

Alternatively, as shown in the embodiment of FIGS. 7-9, where likereference numbers have been used for like parts, the feed shoe mayinclude a removable heating hopper 160. In this embodiment, instead of asolid main body, the feed shoe has a plurality of upright supports 162extending upward from a flat, horizontal metal plate 164 to support thetop surface 166 of the feed shoe 168. The top surface has a bore 170between the supports 162. The supports 162 are spaced apart a distancesufficient to receive the heating hopper 160 between them.

Outboard of the supports 162 and connected thereto are a pair of guidepost supports 172 which hold outwardly extending roller guide pins 174which fit beneath horizontal guide rails 176 which are supported byguide rail supports 178 secured to the wear plates 74 on the table 12.The roller guide pins control the path and downward clamping force ofthe feed shoe. A similar arrangement of horizontal guide rails 176 andguide rail supports 178 are used in the first illustrated embodiment,although in that embodiment the roller guide pins 174 may extenddirectly out from the sides 179 of the feed shoe main body 104, as shownin FIG. 2.

In the embodiment of FIGS. 7-9, the same numbers as used with respect tothe embodiment of FIGS. 1-5 have been used for the bridge 38 althoughthe side walls 72 extend upward from the horizontal guide rails 176 inthe embodiment of FIGS. 7-9. As in the embodiment of FIGS. 1-5, a flange76 is used to connect the movable feed tube (not shown in FIGS. 7-9),although the top plate 70 of the bridge need not allow for pivoting ofthe flange as in the preferred embodiment of FIGS. 1-5.

The removable heating hopper 160 illustrated in FIG. 9 is annular, witha central bore 180 and an outer sleeve carrying a heating element. Inthe illustrated case the heating element is a fluid flow path 182 withan inlet 184 and an outlet 186 connected by conduits 188, 189 to asource of heated oil (not shown).

Generally, the feed shoe of the first illustrated embodiment may bepreferred for larger parts to be produced, as it allows for a largerbore or hopper volume, thereby allowing more material to be held in thefeed shoe, and thereby allowing for the production of larger parts. Ineither embodiment it may be desirable to use a heat-conductive insert inthe central bore to decrease its volume for some applications.

Regardless of the type of heating system used, and regardless of whetherthe delivery system even includes a heating element, the delivery systemof the present invention may use a valve 24 such as that shown in FIGS.10-14 as a means for selectively allowing raw material to pass from saidvertically fixed tube through the vertically movable feed tube. As thereillustrated, the valve 24 is part of the fixed vertical feed tube 22,the entirety of which can be considered to be the valve. At or near thetop end 23 of the vertical feed tube 22 there is a pivotal ring 190surrounding the vertical tube 22 and capable of pivoting about thecentral vertical axis 90 of the tube. The pivotal ring 190 is connectedthrough elongate interconnecting posts 192 to a pivotal end gate 194,which is also pivotable about the central vertical axis 90 of the tube.Above the pivotal end gate is a fixed apertured member 196 attached tothe sides of the tube 22 by a series of cap screws or the like. The gateand apertured member are connected together at their centers by a post197 that allows the pivotal end gate 194 to pivot.

The illustrated fixed apertured member 196 has three cutouts 198A, 198B,198C separated from each other by 45 degree increments. The threecut-outs 198A, 198B, 198C provide three defined volumetric openings forallowing raw material such as powdered metal to pass therethrough. Thepivotal end gate 194 has three orifices 200A, 200B, 200C that arecomplementary in size and configuration to the cut-outs 198A, 198B, 198Cof the fixed apertured member 196. In the illustrated embodiment, toopen the valve, the pivotal end gate 194 is pivoted to a positionwherein its orifices 200A, 200B, 200C are aligned with the cutouts 198A,198B, 198C by causing the top ring to turn. When the top ring 190 turns,the turning motion is translated to the gate 194 through the posts 192.To close the valve, the pivotal end gate 194 is pivoted to a positionwherein the orifices 200A, 200B, 200C are out of alignment with thecutouts 198A, 198B, 198C, to prevent sifting of raw material through thecutouts and orifices. To ensure positive closure of the valve whendesired, it is preferable that the orifices 200A-C of the gate 194 beslightly smaller than the cutouts 198A-C.

An air actuator 202 is provided in the illustrated embodiment,tangentially connected to the ring 190 at the top 23 of the tube 22 asshown in FIG. 10 so that as the actuator rod 204 is pushed out andpulled back, the ring 190 turns about the axis 90. This turning of thering 190 rotates the gate 194 to align the orifices 200A-C and cut-outs198A-C when the valve is opened and to take them out of alignment whenthe valve is closed.

Other types of valves may be used to control the passage of raw materialfrom the fixed to the movable feed tubes. For example, it may bedesirable to use a pair of slotted plates, one overlying the other andreciprocable over the other between blocked and open positions. As willbe understood by those in the art, other alternative valves could beused, such as a ball valve.

Preferably, the actuator 202 is adjusted to be controlled by theoperation of other parts of the press rather than merely by timing. Oneway of operating the valve and other parts of the raw material deliverysystem of the present invention is shown in FIG. 6A-6E. As illustratedin FIG. 6A, when the table 12 is at its full height and the feed shoe100 is aligned under the tube 28, the valve 24 may be set so as to beopen so that the raw material sifts through the aligned orifices andcut-outs and into the interior passage 45 of the vertically movable tube28. The bottom opening 40 of the feed tube 28 is aligned with thecentral bore 102 in the feed shoe 100, so that the raw material fillsthe central bore of the feed shoe, as shown by the darkened areas inFIG. 6A. When the feed shoe is moved forward so that its central bore102 is aligned with the die cavity 14, the contents of the feed shoebore 102 are dropped into the die cavity. Preferably, the valve actuatoris set to close the valve before the feed shoe moves forward to theposition shown in FIG. 6B. The interior 45 of the vertically movablefeed tube 28 remains filled with raw material because the opening 40 atits bottom end 36 is blocked by the top surface 120 of the feed shoemain body that extends rearward over the tails 106.

Next, as the feed shoe 100 returns to its retracted position beneath themovable feed tube 28, as shown in FIG. 6C, and the table 12 drops forcompaction of the raw material in the die cavity 14, the valve 24remains closed. The first coaxial section 30 of the movable feed tube 28moves down with the bridge and table while the fixed tube 22 and valve24 remain in their vertical position.

Next the compacted part is stripped from the press by moving the tablestill further downward as shown in FIG. 6D. The valve 24 remains closedso the interior 45 of the feed tube 28 does not overfill. The firstcoaxial portion 30 of the movable feed tube 28 continues to telescopedown, exposing greater parts of the fixed tube 22. The length of thefirst coaxial portion 30 is great enough so that when the table is atits lowest, at least the valve 24 and bottom end of the fixed tube arestill within the cylindrical first part 30 of the movable tube 28. Theinner diameter of the first coaxial portion 30 is great enough so thatit may slide up and down over the valve 24, including the pivotal gate194 and posts 192.

Next, the table 12 cycles back to the original raised position, as shownin FIG. 6E, raising the vertically movable feed tube 28 so that thefirst coaxial portion 30 moves up the fixed tube 22. The valve 24 isready to open to fill the interior 45 of the vertically movable feedtube 28.

Thus, in the illustrated embodiment, the actuator is controlled to openthe valve 24 when the table 12 is up and the feed shoe 100 is in theretracted position beneath the vertically movable feed tube. At allother times, the valve is preferably closed. Generally, the valve shouldbe open when the table is at its highest position and preferably closedbefore the table drops away from this position.

Position switches (not shown) may be located both over the die area andin the full retract positions. For example, it is preferred to haveswitches to sense the position of the feed shoe to ensure that the pressdoes not impact the feed shoe. For this purpose, there may be oneposition switch over the die to sense whether the feed shoe is present,and another switch may be disposed to detect when the feed shoe is inthe retracted position as a fail safe in case of failure of the firstswitch.

It may be desirable to include a powder level sensor (not shown) in theinterior passage 45 of the vertically movable feed tube 28 below theposition of the valve to control the operation of the valve 24. Thevalve 24 could be set to open, for example, only when the powder levelfalls below a pre-set level. Such a control could be independent of thepositions of the table and feed shoe, or could be used in combinationwith valve controls based on the table and feed shoe positions.

As will be understood from this description of the operation of thedelivery system, it is not necessary that the vertically movable feedtube 28 have the two portions 30, 32 as shown in the attached drawings.The entire vertically movable feed tube 28 could be coaxial with thevalve 24 and fixed feed tube 22. However, by providing the two sectionsof the movable feed tube 28 as described, so that the central axis ofthe bottom hole 40 is different from the central vertical axis 90 of thefixed tube 22, the movable feed tube 28 may be pivoted to block or drainit as shown in FIG. 5 without disconnecting the fixed and movable tubes22, 28 from each other. This feature is particularly advantageous whenchanging the raw material, such as when changing to a different metalpowder, to make the changeover relatively fast and easy. To furtherfacilitate the changeover, it may be desirable to provide a manualoverride on the valve so that it may be manually opened for draining theraw material from the system.

And although different structures for the bridge 38 have beenillustrated and described, it is advantageous if the distance betweenthe side wall supports 72 is greater than the opening in the table toreceive the die so that the die may be easily removed and changed.

It should be understood that the raw material delivery system of thepresent invention may be used with presses operating on room temperatureor temperature-controlled materials. The illustrated embodiments areparticularly useful when making parts from warm metal powder. To warmthe powder to the desired temperature, the illustrated embodimentprovides a pre-heater 20 which may be an oil-heated cylinder within anouter sleeve surrounding an inner cylinder within which the raw materialmay be carried. To keep the raw material from cooling while in the valveor vertical tube 22, the walls of the tube may be heated by an electricheater 220 comprising resistors adhered to the outer surface of the tube22. Other means for heating the contents of the vertically fixed tubemay be used; it may be possible to heat the vertically fixed tube with aliquid, such as hot oil, flowing into and out of a jacket, through aninlet and outlet positioned so as to not interfere with movement of thevertically movable feed tube 28.

In the first illustrated embodiment, the tube 22 may be made of roundmechanical tubing drawn over a mandrel and welded with, for example, a13 gauge wall thickness.

In the first illustrated embodiment, at least a portion of thevertically movable feed tube 28 is heated by a flow of heated oilthrough the cavity 48 between the exterior 46 and interior 44 walls ofthe second section 32 of the vertically movable tube 28. The main body104 of the feed shoe 100 surrounding the central bore 102 may also beoil-heated, as may be the removable heated hopper 160 in thatembodiment.

The appropriate temperature to which the raw material should be heated,and the appropriate temperature to which the heat transfer medium, suchas the oil, should be heated can be expected to depend on the materialsused. For example, when working with lubricated powdered metal as theraw material, it is important not to have the powder temperature toohigh for a given part, or else the heat generated during the compactingoperation could cause the powder temperature to approach or exceed themelting point of the lubricants admixed with the powdered metals.Operating near or above the critical powder temperature can causeworkpiece ejection problems and streak lines on the finished workpiece.Moreover, the useful life of the compacting tools may be shortened ifthe die temperature and powder temperature become so hot that ejectionof the part becomes difficult.

Suitable lubricated metal powders are available from sources such asHoeganaes under the name “ANCHORDENSE” and from Quebec Metal Powdersunder the name “FLOMET”. When a lubricated powdered metal is used, itspreferred temperature when reaching the die will depend on the type ofpowder, the density desired and the overall length or geometry of thepart. In any case, the preferred temperature range for the powderedmetal is usually below the softening point of the lubricant in thepowder; the preferred temperature range for the powder is typically inthe range of about 180-300° F. The oil heater may be one that maintainsa similar temperature range, at a static oil pressure of, for example,20-40 psig, with a rate output of, for example, at least 122,800 BTU/Hr.As shown in FIG. 1, the oil heater, or source of heated oil 54, maydeliver heated oil at this temperature and pressure to the pre-heaterheater 20, the vertically moveable tube 28 and the feed shoe body 104 orhopper 160. The temperature of the electric heater 220 on the fixed tube22 may be set for a similar temperature range. It may be desirable toprovide for setting the pre-heater 20 at a lower temperature to preventcaking. A solenoid valve, for example, could be provided for separatecontrol of the flow of hot oil for such zone heating of the pre-heateror other part. It may also be desirable to provide for heating the die,which may also be set at a slightly lower temperature. A system such asthat illustrated may, for example, provide about 750 pounds of powderper hour to the compacting press.

The materials selected for the parts designed to serve as heat exchangesurfaces should be selected to be effective for that purpose. Forexample, stainless steel is a relatively poor heat transfer material,and is preferably not used for the interior wall 44 of the verticallymovable tube 28. Instead, a preferred material is a standard thin walledsteel tube of good thermoconductivity and weldability. For example, aone-eighth inch thick mild steel material may be used. In addition, thefeed shoe main body of the first illustrated embodiment may be made ofaluminum for example.

It should be understood that other heat exchange structures can also beused. For example, for the pre-heater 20, a heat exchanger such as thatshown in FIGS. 16-17 may be used. That structure has heated oil flowingnot only through an outer sleeve 230 but also through an interior finnedheat exchanger 232. The raw material such as the powdered metal dropsthrough passageways 234 between the fins 236. As in the verticallymovable tube 28, the fixed tube 22, and the feed shoe main body 104, themetal powder fills from the bottom up, and it is desirable to utilize areverse flow of heated material such as the heated oil, so that thepowder closest to the exit of each of the heaters is the hottest.

In operation, care should be taken in setting the fill levels, as wellas using and timing the core rod in the up position. During operation,the valve 24 will allow the vertically movable feed tube 28 to fill tothe bottom of the valve when the valve is in the open position, and thefeed shoe 100 will accept powder from the vertically movable feed tube28 when the feed shoe is in the retracted position, lowering the levelof powder in the vertically movable feed tube and allowing additionalpowder to fall into the vertically movable feed tube 28 through thevalve 24 from the vertically fixed feed tube 22. If the fill level isincreased, powder could compact under the valve and cause damage to thevalve assembly unless the powder is drained from the vertically movabletube prior to the change in fill level.

Care should also be taken if using the core rod “up” position in thepress. In the heated applications, the feed shoe may contain pressurizedhot oil, and the core rod should not come into contact with the feedshoe main body. If the core rod goes above the height of the die, itcould either prevent the feed shoe from properly filling the die, orprevent it from returning to the retracted position. The limit switchesshould pick up any mistake prior to the upper punch causing damage, butthe integrity of the feed shoe could be broken, causing hot oil to spillonto the table. The core rod could also damage the wear pad on the feedshoe if it makes contact. If the core rod in the up position is used,accurate timing of the equipment is necessary.

If it is necessary to change the die for a new part to be produced forexample, the feed shoe may be removed for easy access to the cavity inthe table. If the same powder is going to be used, the verticallymovable feed tube may be pivoted to the position where the bottom end isblocked by the horizontal plate of the bridge (see FIG. 5B). If adifferent powder is going to be used, a drain cup can be placed on thedrain cut-out 82 on the bridge 38, the source of the old metal powdercan be removed, the vertically movable tube 38 can be pivoted to thedrain position (see FIG. 5C), and the remaining powder can be allowed todrain into the drain cup and then stored for later use.

In the embodiment of FIG. 18, the press apparatus 300 includes a table302 with a horizontal surface 304, and an opening or cavity 303 in thehorizontal surface for raw material to be delivered to the die 305, asin the first illustrated embodiment. As shown in FIG. 18, the table 302is vertically movable and is in a plurality of vertical positions ineach cycle of operation of the press apparatus 300. The system forheating raw material and delivering raw material to the die includes afeed shoe 306, which has a central bore 308, and may be substantially ofthe type shown in the first illustrated embodiment. The feed shoe 306 ismovable in a direction parallel to the horizontal surface 304 of thetable 302, and also moves vertically with vertical movement of the table302 so that the feed shoe is in a plurality of vertical positions ineach cycle. The retracted position of the feed shoe 306 is shown insolid lines in FIG. 18 and the extended position is shown in phantom.

The second embodiment of the press apparatus and system for heating anddelivering raw material also includes a tube or transfer element 310that has top and bottom openings 312, 314 and a passage 316 extendingbetween the openings. In the embodiment illustrated in FIG. 18, the tubeor transfer element 310 comprises an intermediate hopper line, and maybe heated or not heated. The transfer element 310 is fixed with respectto the table, and maintains a vertically fixed position with respect tothe table throughout the cycle. Any suitable mounting bracket or otherstructure may be used to position the transfer element. As in the firstembodiment, the FIG. 18 embodiment also includes an enclosure 320 with abore 322 through which raw material may pass. The enclosure 320 extendsfrom the upper surface of the feed shoe 306 to the vertically-fixedelement 310. As in the first embodiment, means for heating the rawmaterial before the raw material reaches the feed shoe are alsoprovided.

In the embodiment of FIG. 18, the enclosure 320 comprises an elongateflexible hose that is fixed to the feed shoe 306 and to thevertically-fixed transfer element 310. The bore 322 of the enclosure 320is defined by a flexible open inner conduit having a smooth inner wall.In the illustrated embodiment, the inner conduit is made of “Teflon”brand polytetraflouroethylene and has an inside diameter of about 1¼inches. The inner conduit is surrounded by sleeves of stainless steelbraid (not shown) over which is wound a wire electrical heating element323 surrounded by thermal insulation (not shown), vinyl tape (not shown)and an outer polyester sleeve 325; a temperature sensor (not shown) iswithin the hose, and layers of vinyl tape (not shown) are between theelectrical heating element and the stainless steel braid and between theelectrical heating element and the temperature sensor. Thus, theenclosure includes the means for heating the raw material. The combinedenclosure and means for heating the raw material may be a commerciallyavailable product, the 501 Series Heated Transfer Hoses available fromSlautterback Corporation of Monterey, Calif. and the Illinois Markingand Sealing Division of Glennon Corp. of Elk Grove Village, Ill. In theillustrated embodiment, the elongate flexible hose is operable attemperatures in the range of 201-450° F., has an outer diameter of 1½inches, has male threaded stainless steel end fittings, a length of fourfeet, a thermocouple type of temperature sensor, is operable at 115 V,and has a polyester expando outer sleeve. The elongate flexible hose isdescribed in publication no 4K 07/97 of the Slautterback Corporation,which is incorporated by reference herein. The elongate flexible hosecould also have female fittings. It should be understood that thisparticular elongate flexible tube is identified for purposes ofillustration only, and that other devices may be used. The elongateflexible hose extends between the feed shoe and the tube so that whenthe feed shoe is in the retracted position, raw material may pass fromthe vertically-fixed tube into the elongate flexible hose and may passfrom the elongate flexible hose into the feed shoe substantially freefrom exposure to a cross-flow of air. And since the inner surface of theflexible inner conduit is smooth rather than accordion-pleated, there isless chance for the warm powder to gather and become blocked.

As shown in FIG. 18, the feed shoe 306 and bottom part 330 of theflexible hose move vertically with vertical movement of the table 302and are in a plurality of vertical positions in each cycle. The top part332 of the flexible hose remains coupled to the vertically-fixedtransfer element 310 throughout the cycle and is vertically fixed withrespect to the table 302 throughout the cycle.

It should be understood that parts of the feed shoe are not shown inFIG. 18, and that elements of the feed shoes of the other embodimentsmay be used with the present invention. Other feed shoe designs may alsobe used.

While only specific embodiments of the invention have been described andshown, it is apparent that various alternatives and modifications can bemade thereto. Those skilled in the art will recognize that certainmodifications can be made in these illustrative embodiments. It is,therefore, the intention in the appended claims to cover all suchmodifications and alternatives as may fall within the true scope of theinvention.

We claim:
 1. In a press operable in cycles for compacting raw materialin a die to produce a product in each cycle, the press being of the typehaving a table with a horizontal surface and an opening in thehorizontal surface for raw material to be delivered to the die, a systemfor heating raw material and delivering heated raw material to a diecomprising: a feed shoe having a central bore, said feed shoe beingmovable in a direction parallel to the horizontal surface of the table;a vertically-fixed transfer element having top and bottom openings and apassage extending between the openings, the vertically-fixed transferelement being supported independent from the table; wherein said feedshoe is movable on said table to a retracted position and an extendedposition wherein the central bore is aligned over the die; means forheating said raw material before the raw material reaches said feedshoe; and an enclosure with a bore through which raw material may pass,said enclosure extending between said feed shoe upper surface and saidvertically-fixed transfer element so that when said feed shoe is in saidretracted position material may pass from said vertically-fixed transferelement bottom opening to said enclosure and from said enclosure to saidfeed shoe central bore substantially free from exposure to a cross-flowof air; the table being vertically movable and being in a plurality ofvertical positions in each cycle, the feed shoe and at least part of theenclosure moving with the vertical movement of the table to be in aplurality of vertical positions in each cycle, the vertically-fixedtransfer element maintaining a vertically fixed position with respect tothe table throughout the cycle.
 2. The system of claim 1 wherein thebottom opening of said vertically-fixed transfer element istelescopically received within said enclosure throughout the cycle. 3.The system of claim 1 wherein the enclosure comprises a flexible hoseconnected at one end to the vertically-fixed transfer element and at theopposite end to the feed shoe.
 4. The system of claim 3 wherein themeans for heating said raw material before the raw material reaches saidfeed shoe comprises an electrical heating element on the flexible hose.